She was the love of his life, the fire behind his lines. For 52 years Véra Nabokov devoted her life to her husband's work, and he dedicated his books to her. It was Véra, according to her biography, which is published today, who plucked Nabokov's manuscript of Lolita from the flames when he discarded it, listened to him reading the drafts, typed as he dictated and proofread every single book. So behind every author's thanks to his or her spouse for "their love and support, without which the book could not have been written" lies another story of how that relationship sustained, and survived, the book.

For the last three years I have been living with Rudyard Kipling - my partner, Andrew Lycett, is his biographer. Having nurtured him patiently through two other biographies, I now have a certain empathy with Kipling's wife, Carrie, who advised a friend: "I would not marry a literary man for worlds, they are always doing too much, and one can only give them help by being hopelessly dull..."

People often imagine life with an author to be "fascinating". "Demanding" would be a more accurate description. The book takes priority over everything. Any idea of "partnership" is a distant dream when it is often the non-writer doing the work. Try discussing your day with someone who often has talked to no one else; try getting up every morning to go to work while your loved one is still in bed "thinking". "There is a lot going on in his head that I'm not privy to," says American lawyer Barbara Shacochis of her husband, novelist Russell Celyn Jones. "He can't just turn on and off."

Books are like babies; they have a long gestation period, followed by a delivery date. As many authors work from home, the creative output is reliant on a supportive mate. After 39 years of marriage to author Penny Vincenzi, her husband, Paul, sees his role as "author's therapist, mainly listening until Penny arrives at her own conclusions, and only offering suggestions in emergencies".

And, like many a new father, the author's partner can often feel marginalised once the book is out - left out while the author metamorphoses from a monosyllabic, distracted companion into a wild party animal, caught up in a whirl of soirées, tours and signings.

Few authors manage to get the advances of Jeffrey Archer, so partners should also be able to provide that vital second income, which is essential to maintain the writer and family above the poverty level. Having to shoulder all the everyday problems alone is also common, a situation which allows the writer to work unencumbered by the trivialities of life, such as organising the household and paying the bills. "As deadlines approach, the washing-up tends not to get done," says Kathy Lette's husband Geoffrey Robertson QC - obviously not fully understanding his supporting role.

Like Véra Nabokov, partners may also be required to read manuscripts and offer helpful suggestions. Robert Harris's wife, Gill Hornby, is his first reader. "It would be difficult to know what to say if they weren't good," she says. "There is often a dark cloud around when things are going wrong, and tension when the reviews are due out."

Because an author's thoughts are frequently elsewhere, partners may also have to endure silent meals, and forego holidays and a social life when deadlines loom. "Sometimes Robert becomes so focused he goes a bit barmy and does things like putting his socks in the fridge," says Hornby. "We rarely have holidays because when Robert's not working he doesn't feel he needs a break, and when he is writing he hasn't got the time."

Rarely is a writer truly happy. With no colleagues to help dispel worries, the stress seeps out from under the study door and pervades the whole house. Happiness is often dependent on receipt of an advance, or a new idea or the moment when a book is finished. But euphoria is shortly followed by the feeling of loss for the characters who have become friends and family, anxieties about reviews and sales figures, and the stress of wondering what to write next.

Writing is a cyclical and often lonely occupation: any spare time is spent combing the bookshops to make sure the author's books are in stock, and moving them to the most advantageous position on the shelves. (Some literary spouses, such as the woman caught in the window of a New York bookstore substituting the main display with her husband's little-known biography, get infected by their partner's obsession.)

For Ellen Frey, marriage to Frank McCourt in 1989 began at almost the same time as his book. Two months after the wedding he started writing Angela's Ashes. "Every day in bed he read to me what he had written," says Frey. The book's success has changed her life as much as his. They have more money but, sometimes, Ellen says, she resents the intrusion of an office into their home. Life became so hectic from the numerous spin-offs, invitations and correspondence that Ellen gave up her PR job to travel with Frank as his "social secretary".

In dedicating Love in the Time of Cholera to his wife with the words "For Mercedes, of course", Gabriel Garcia Marquez acknowledged the part she played in its creation. Although Nabokov dedicated his books to Véra, he refused to say how important she had been as a collaborator. So if you are still thinking of living with a writer, don't expect thanks and don't look to them for help, companionship or entertainment - except, that is, after the last full stop has been written.

 Véra (Mrs Véra Nabokov): A Portrait of a Marriage by Stacy Schiff is published today by Picador at £25.